전처리 Pass 추가

 add_llvm_library( LLVMObfuscation MODULE
   ReturnObfuscation.cpp
+  PreProcess.cpp
 
  DEPENDS
  intrinsics_gen

+#include "llvm/Pass.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/Support/Alignment.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/IR/CFG.h"
+#include <fstream>
+#include <iostream>
+using namespace llvm;
+
+namespace {
+    struct PreProcess : public FunctionPass {
+        static char ID;
+
+        PreProcess() : FunctionPass(ID) { }
+        bool runOnFunction(Function &F) override {            
+            Module* mod = F.getParent();
+            std::vector<Instruction *> instructions;
+            std::vector<BasicBlock *> RetBlocks;
+            bool inserted = false;
+            std::ofstream functionFile("functions.txt", std::ios_base::app);
+            if (functionFile.is_open()) {
+                functionFile << F.getName().str() << "\n";
+                functionFile.close();
+            }
+            for (auto &BB : F) {
+                for (auto &I : BB) {
+                    if (I.getOpcode() == Instruction::Ret) {
+                        instructions.push_back(&I);
+                    }
+                }
+            }
+            for (auto &I : instructions) {
+                BasicBlock *BB = I->getParent();
+                // One Instruction Basic Block has only one ret instructions
+                if (!BB->size() < 2)
+                {
+                    BasicBlock *retblock = BB->splitBasicBlock(I->getIterator(), "obfuscatedreturn");
+                } else {
+                    BB->setName("obfuscatedreturn");
+                }
+            }
+            return true;
+        } 
+
+    }; // end of struct Hello
+}  // end of anonymous namespace
+
+char PreProcess::ID = 0;
+
+static RegisterPass<PreProcess> X("preprocess", "Hello World Pass",
+                             false /* Only looks at CFG */,
+                             false /* Analysis Pass */);
\ No newline at end of file